1. Field of the Invention
The present invention relates to an electrostatic capacity-type sensor for detecting a deformation based on a change in the electrostatic capacity between a pair of electrodes.
2. Description of the Related Art
According to an electrostatic capacity-type sensor, utilizing a change in electrostatic capacity associated with a change in distance between a pair of electrodes, a compressive deformation can be detected. For example, Japanese Unexamined Patent Publication (KOKAI) No. 5-288619 discloses an electrostatic capacity-type tactile sensor including a pair of metal electrodes facing each other across a space. Further, Japanese Unexamined Patent Publication (KOKAI) No. 2005-315831 discloses an electrostatic capacity-type pressure sensor in which electrodes made of conductive cloth are arranged on both the surface of a sheet-shaped dielectric.
According to the electrostatic capacity-type sensor disclosed in Japanese Unexamined Patent Publication (KOKAI) No. 5-288619, a high dimensional accuracy is required in the distance between the electrodes, so that the manufacturing cost is high. Further, a metal material is used in the electrodes. The metal electrodes have little expansion/contraction properties, so that, for example, when the electrode is bent, the electrode is easy to be broken due to plastic deformation. Also, when the electrostatic capacity-type sensor is formed by placing an elastically deformable dielectric between the metal electrodes, the dielectric can be deformed by bending, but the electrodes cannot follow the deformation of the dielectric. Hence, the electrode and the dielectric are separated from each other, so that the use of them cannot be repeated. In such away, the electrostatic capacity-type sensor including the metal electrodes is not suitable to detect the bending deformation. Further, the sensor is difficult to be attached to a curved shape.
On the other hand, the electrostatic capacity-type sensor disclosed in Japanese Unexamined Patent Publication (KOKAI) No. 2005-315831 uses an electrically-conductive cloth (conductive cloth) for the electrodes. The conductive cloth has expansion/contraction properties. However, the expansion/contraction direction is restricted by weaving method. Further, the conductive cloth has a stitch, so that the area of the electrode becomes small by the clearance of the stitch to cause the electrostatic capacity to become small.